What is the role of radial optic neurotomy (RON) in the treatment of central retinal vein occlusion (CRVO)?

Radial optic neurotomy (RON)
[52, 53, 54, 55, 56, 57] is a new surgical technique in which a microvitreoretinal blade is used during pars plana vitrectomy to relax the scleral ring around the optic nerve. The central retinal artery and vein passes through the narrow openings of the cribriform plate in the optic disc.

Promoters of this technique suggest that CRVO may be due to the compression of the central retinal vein at this location creating a compartment syndrome. If this procedure is successful, it decompresses the closed compartment and leads to an improvement in venous outflow and a reduction of macular edema.

In one study, RON resulted in clinically relevant improvements on a long-term basis. Patients with nonischemic CRVO may respond more favorably than patients with ischemic CRVO.

In another study, significant improvements were observed in the b-to-a ratio of the standard combined ERG after surgery in eyes with CRVO.

The benefits from surgery have not been clearly documented. One study, looking into the biomechanical effect of RON, found negligible change in the space around the central retinal vein; RON is unlikely to be a procedure that could mechanically ameliorate the clinical sequelae of a central vein occlusion. The improvement of retinal function is most likely due to improved oxygenation of the retina caused by vitrectomy and not by RON.

In addition to the regular complications of vitrectomy, RON can result in significant hemorrhage and neovascularization at the incision site.

No consensus currently exists among various researchers regarding the exact criteria for the use of RON.

Peripheral fundus view of the same patient with central retinal vein occlusion as in the previous image, showing hemorrhages extending all over the fundus.

Fluorescein angiograph of same patient with central retinal vein occlusion as in previous images, showing hypofluorescence due to blockage from hemorrhages in the retina. It is not useful to perform a fluorescein angiogram in acute stages of the disease.

Fundus picture of the same patient with central retinal vein occlusion as in previous images, showing resolving neovascularization of the disc and panretinal photocoagulation scars.

Fluorescein angiogram of the same patient with central retinal vein occlusion as in the previous images, taken more than 1 year later, showing persistent cystoid macular edema with good laser spots.

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